Many commercial processes generate wastewater and/or lead to contamination of groundwater, lakes, streams, and rivers. Mine tailings such as slurry contain a large proportion of water, and cooling waters for blast furnaces used in iron and steel processing are often contaminated with polycyclic aromatic hydrocarbons, ammonia, cyanide, acids, iron, and related chemical species. The chemical industry produces large amounts of wastewater that may be contaminated with intermediates from chemical synthesis, plasticizers, and end products including pharmaceuticals, pesticides, and the like. Water from agriculture and the food processing industry can contain large amounts of organic matter as well as potentially harmful microbial species such as those found in the intestinal tracts of animals slaughtered for meat. Additionally, municipal wastewater may contain microorganisms, detergents, surfactants, trace pharmaceuticals, and other contaminants. Further, wastewater must either be stored, which can be expensive and can require a great deal of space, or else it must be processed so that it is safe prior to discharging it back into the environment.
Contaminants in wastewater can negatively impact human health. As more livestock animals are treated prophylactically with antibiotics, antibiotic-resistant bacteria are becoming more common. These may find their way into the water supply via faulty processing at meat-packing plants. Antibiotic resistance is a serious threat to public health and is responsible for many hospitalizations and deaths each year. Water-borne pathogens, on the other hand, are especially problematic in developing countries without adequate sanitation and/or water treatment facilities, as well as in remote areas where residents must rely on well water for drinking, washing, and cooking. Other contaminants in water supplies include carcinogens (e.g. pesticides, plasticizers, polycyclic aromatic hydrocarbons), heavy metals, and endocrine disruptors; these are responsible for a wide range of health problems in both humans and domestic animals. Even absent the aforementioned contaminants, particulate matter can render drinking water cloudy and can interfere with the taste and smell of the water. Further, dissolved organic material can provide nutrients to algae and other aquatic microorganisms, thus leading to toxic algae blooms, which prevent recreational use of waters and which can cause harm to fish and other seafood populations.
A variety of devices designed to purify water are already on the market for home user. These include filters for refrigerators, taps, water pitchers, and the like, as well as whole-house systems that make use of ultraviolet disinfection, reverse osmosis, and related techniques. However, these devices are often expensive to install, require costly replacement parts at regular intervals, and are not practical solutions to water quality problems in areas that lack municipal water supplies and/or consistent and reliable sources of electricity.
Various methods of treating municipal water, well water, and wastewater are known in the art. For example, chlorine and/or iodine tablets can be used to disinfect small amounts of water for personal use. While effective at killing bacteria, these tablets do not remove heavy metals, organic matter, or particulate matter from water. Further, depending on the mineral content of the water, chlorine- and iodine-based disinfection can lead to discoloration and/or taste changes that make the treated water unpalatable.
Several polymeric systems have been proposed as flocculants or clarifying agents to be used in water treatment. However, these often have undesirable side effects. For example, metal ion/polysaccharide systems containing silver ions may not be desirable for treatment of drinking water due to expense and to the tendency of silver ions to bioaccumulate, causing skin discoloration and even silver poisoning. Aluminum-containing coagulants may contribute to developmental and/or neural toxicities, especially in acidic environments. Other polymer-based water purification systems require numerous additional components such as clays, chlorine-based disinfectants, pH-altering ingredients, metal salts, and the like. The high number of ingredients or components in such systems increases the expense associated with water purification as well as the required skill level of the worker performing the purification. Additionally, some polymers used in water-purification processes suffer from solubility problems or are required in high amounts to be effective.
It would thus be desirable to develop an inexpensive, safe, and easy-to-use system for purifying well water, municipal water supplies, and/or wastewater.